Ignition devices for propulsion engines of the continuous combustion type



Filed Jan. 27, 1958 P. F. GREEN ETAL IGNITION DEVICES FOR PROPULSION ENGINES OF THE CONTINUOUS COMBUSTION TYPE 2 Sheets-Sheet 1 Feb. 14, 1961 P. F. GREEN ETAL 2,971,340

IGNITION DEVICES FOR PEOPULSION ENGINES OF THE CONTINUOUS COMBUSTION TYPE Filed Jan. 2'?, 1958 2 Sheets-Sheet 2 Unite States Patet 2,971,340 Patented Feb. 14, 1961 ice IGNITIGN DEVC'ES FOR PROPULSION ENGINES F THE `Ct'JltITIlltJUQUS COMBUSTIN TYPE Percie Francis Green and Leslie George Bullock, Bristol, England, assignors, by mesne assignments, to vlristoi Siddeley Engines Limited, Bristol, Engiand, a British company Filed Jan. 27, 1958, Ser. No. 711,344

Claims priority, application Great Britain Jan. 30, 1957 Claims. (Cl. 60-39.82)

This invention relates to ignition devices for propulsion engines of the continuous combustion type.

in the patent specification tiled with patent application No. 657,174, now abandoned, there is described a reigniting device for use with the combustion chambers of continuous combustion engines for mitigating the eiects of ilame quenching or blow-out which are occasionally encountered due to a transient disturbance in the flow of working lluid through the engine or in the supply of fuel to the engine.

The reigniting device includes a body of refractory material carried by a mounting so as to lie in the zone of primary combustion and be immersed in ame dur ing normal operation of the combustion chamber and to become heated to a temperature above the spontaneous ignition temperature of the fuel being used, the mass of said refractory material which becomes so heated being of sufficient heat capacity in relation to the heat losses which occur from the body during periods of operation without combustion that during a transient disturbance in the ow of working iluid through the engine or in the supply of fuel to the engine which causes a blowout, the body retains a suiiciently high temperautre to be capable of reigniting the fuel immediately after the llame quenching effect of the transient disturbance has ceased.

For convenience, in the present specification, a body of refractory material having capabilities as above stated when appropriately used, together with any parts rigidly attached to it, will lbe referred to as a rei-gniter member.

The present invention broadly provides a reignition device comprising a carrier member and a reigniter member carried thereby so as to be movable between an inoperative position and an operative position in relation to the carrier member, the carrier member `being adapted for attachment to a wall of a continuous combustion combustion chamber in a manner such that when the reigniter member is in its operative position it is Withdrawn from within the combustion chamber or projects from the carrier member into the combustion chamber to a substantially lesser extent than when in its operative position, the reigniter member when in its operative position having its or a refractory material part lying within the combustion chamber.

It will be appreciated that in use the reignition device is attached to the wall of the combustion chamber at a position such that the reigniter member, when in its operative position has its or a refractory material part lying in the zone of primary combustion of the combustion chamber so as to be immersed in flame during normal operation of the combustion chamber.

Since in its inoperative position the reigniter member is exposed to less heating, by retracting the reigniter member from its operative position to its inoperative position when its use is not likely to -be required, the useful life of the reigniter member may be substantially increased, or a material less resistant to prolonged high temperatures may be used for its construction.

In the preferred form, the carrier member comprises a housing having a straight bore, and the reigniter member comprises a root part slidably mounted in said bore.

Preferably also, said root part and said bore constitute a retraction piston and cylinder assembly whereof the piston is displaceable relative to the cylinder by iluid under pressure to move the reigniter member from its operative to its inoperative position.

According to a further feature of the invention, said cylinder may have a port for communicating the interior of said cylinder with the interior of a continuous combustion combustion chamber to which the reignition de vice is to be attached, whereby the pressure of gas in the combustion chamber is permitted to act on said piston to urge the piston in the direction to retract" the reigniter member from its operative to its inoperative position.

It will be understood, of course, that a reignition device as last defined is intended 4for use in conjunction with a continuous combustion combustion chamber which operates at an internal pressure exceeding the external pressure.

A further preferred feature is that the reignition device comprises motive means operable by fluid under pressure to project the reigniter member to its operative position.

Said motive means may comprise a projection piston and cylinder assembly whereof the piston has the same piston area as said yfirst said piston and cylinder assembly.

Thus in one arrangement the retraction piston may also constitute the projection piston.

Alternatively, however, said motive means may comprise a projection piston of larger piston area than said retraction piston, said projection piston being formed as part of said root part and being slida'ble in a cylinder formed in said housing.

The latter construction is particularly useful where the gas pressure in the combustion chamber is to be used to, move the reigniter member from its operative to its inoperative position and a supply of operating medium at a pressure suiciently above the internal pressure of the combustion chamber is not available for moving the reigniter member in the reverse direction, that is, from its inoperative to its operative position.

The present invention also provides in a continuous combustion engine having a continuous combustion combustion chamber, a reignition device comprising a carrier member mounted on the'wall of the combustion cham-ber, and a reigniter member carried by said carrier member so as to be movable between an operative position in which the or a refractory material part of the reigniter member lies within the combustion chamber in the zone of primary combustion of the combustion chamber and an inoperative position in which the reigniter member is-withdrawn from within the combustion chamber or projects from the carrier member into the combustion chamber to a substantially lesser extent than when in its operative position.

Where such an installation, or an aircraft or other vehicle of which it forms a part, is provided with protective equipment, as for example an anti-icing or tie-icing device, which has to bemaintained in operation when conditions are such that it is desirable that the reigniter member should also be in its operative position, the initiation of operation of `the protective equipment and of movement of the reigniter member from its inoperative position to its operative position may be effected by a single manually or automatically moved control member.

The present invention will now be further described,

merely by way of example, with reference to the accompanying drawings whereof:

Figure 1 is a plan view of a reignition device according to the invention,

Figure 2 is a section corresponding to the line 2-2 of Figure 1,

Figure 3 is a section corresponding to the line 3--3 of Figure 1,

Figure 4 is a somewhat diagrammatic cross-sectional representation of a gas turbine engine incorporating reignition devices according to the invention,

Figure 5 shows details of control means for effecting ro'eotion and retraction of the reignition devices of the P l, .a

engine shown in Figure 4, j

Figure 6 is a cross-section on line 6 6 in Figure 4, and

Figure 7 is a detailed view partly in cross-section showing part of the engine of Figure 4.

Referring 4first of all to Figures 1 to 3, the reignition device comprises a carrier or housing made in two parts 1 and 2 secured together by bolts and nuts 3, 4. The part 1 of the housing is provided with a flange 5 by which it may be attached by bolts 6 to a mounting 7 forming part of the wall 8 of a combustion chamber. The cornbustion chamber is of the kind comprising an inner llame tube 9 in the interior of which combustion takes place, the flame tube being separated from the wall 8 by a passage V10 through which a flow of cooler dilution air is maintained. The assembly includes a hollow locating plug 11 comprising a sleeve part 12 bridging the passage iti and a flange part 13 which is interposed between the mounting pad I7 and the ange 5 of the housing. The housing part 1 is formed with a straight bore 14 in alignment with the axis of the locating plug 11, this axis being directed towards the interior of the combustion chamber. A reigniter member 15 comprising an operative part in the form of an open-ended tube 16 is slidably mounted in the bore 14 by means of a hollow root part 17 enlarged at 18 to constitute a piston tting the bore, sealing being `'efieoted by means of a piston ring 19. The tube 16 projects into the hollow interior of the roo-t part 17 and is there plugged by -a plug 6@ and provided with an exteranl collar 61, the three parts being secured together by cross pins V62. The collar 61 rests on an abutment shoulder 63 at the :end of the root member, and the remainder of the hollowinterior of the latter is lled with a solid material 64 which is a poor conductor of heat. The open end of the bore 14 communicates with the interior of the combustion chamber and constitutes a port through which gas pressure in the combustion chamber is communicated to the lower face of the piston 1S in Figures 2 and 3.

The root part 17 Ais further enlarged at its end furthest from the tube 16 to form a second piston 2t? of larger arca lthan the piston 13, the piston 2@ sliding in a .bore 2i formed in the part 2 of the housing and being sealed by a piston ring 22. The space between the pistons is vented to -the surrounding atmosphere by a number of ponts or holes 23 formed in the part 1 of the housing so that the reigniter member 15 is free to be displaced along a straight line outwardly from the combustion chamber to its inoperative or retracted position, shown in Figure 3, by gas pressure from Ithe combustion chamber acting on the piston 1S, or, along a straight line7 inwardly against this pressure to its operative or projected position, shown in Figure 2, by compressed air acting on the piston 2i).

Referring now to Figures 4, 5 and 6, air for this purpose is bled-from the `engine upstream of the combustion chamber thruogh a' pipe 31, so that it is not at an inconveniently high temperature, and is led to the space above the piston through `a port Z4 in the housing part 1 (see Figure 3 the-port being suitably formed to receive a pipe connection, andL a passage 25 in the housing part 2. In the vpresent example, two suehpports and passages are provided so thatwhere an engine having a number of combustion chambers, for example, the engine shown in Figure 4, is provided with several reignition devices 30, they may easily be interconnected by air supply piping 26 (see Figure 6) to permit of simultaneous operation.

The engine shown in Figure 4 has eight combustion chambers 42 which are interconnected =to form a so called can-annular ltypeof combustion system. Thus, each pair of adjacent combustion chambers are joined by a canal or duct 43, the ducts 43 allowing for the propagation of flame from one combustion chamber to another. In view of this, alternate combustion chambers only are provided with a reignition device 30. In the event of a blow-out of the flame in all the combustion chambers, those combustion chambers without a reignition device would be relit by propagation of the relit iiame from one of the adjacent combustion chambers.

A contro-l valve, generally indicated at 27 in Figure 5, controls the supply of air from the pipe 31 to the piping 26. The control valve has two positions in one of which, as shown, it connects the piping 26 via a pipe 29 with the atmosphere through a port Sil in the valve, and in the other position it connects the piping 26y via the pipe 29 with the main air supply pipe 3l. The valve is displaced Vto the latter position when it is desired that the reigniter members should be moved into their operative position, and to the former position to allow the reigniter members to retract under the influence of the pressure in the combustion chambers. The valve 27 is a spool valve and is operated by an electrical solenoid 33 under the control of a switch 35 placed at the engine control station. The switch 35 may also initiate the putting into operation of other protective equipment, as for example the admission of operating medium for anti-icing or de-icing equipment for the engine or for other parts of an aircraft or other vehicle propelled by Vthe engine.

With some engines it may be dangerous to allow reignition to take place after the rotational speed of Vthe engine or of some part of it has fallen below a certain value, and in such cases a device responsive to the speed of the engine-part in question should be provided to pre-` Y In'the case of a two spool engine such a device wouldV be made responsiveto the speed of one of the rotary systems.

The speed responsive device of the present example comprises a pressure operated switch 34 (see Figure 5) in circuit with the switch 35, the arrangement being such that only when the pressure operated switch is closed is closure of the switch 35 effective to energise the solenoid 33 to displace the valve 27 to its position communicating the air supply pipe 31 with the piping 26. rl`he pressure operated switch 34 is controlled by the centrifugal pressure head in the piston block chamber 3g (see Figure 7) of the engine fuel pump .52.

The pump -32 is of the multi-cylinder awash plate type in which the output is controlled by changing the tilt of the swash plate by means of a servo piston. The servo piston is not shown in Figure 7, but is connected to adjust the tilt of the swash plate by means of the rod 36 in that figure.

The pump has an overspeed device comprising a diaphragm 37 which, when moved to the left in Figure 7 by pressure supplied through the passage 38 from the piston block chamber 39, adjusts a control valve of the pump servo device to reduce the output-of the pump by adjusting the tilt of the swash plate.

The piston block is indicated at 4b in Figure 7, and,

in well known manner, is provided with a radially disposed passage 40a in communication with the suction side of the pump. By virtue of the passage 40a a centrifugal pressure head is developed in `the chamber 39 during operation of the pump which pressure is proportional to the square of the rotational speed of the pump and therefore ofthe engine, which drives the pump through gearing indicated at 48 in Figure 4,

A pipeline is taken from a port 41 opening into the chamber 39 to the pressure operated switch 34, and the switch 34 is adjusted so 4that the pressure in the chamber 39 is able to hold the switch closed only at engine speeds in excess of a predetermined minimum below which it is not safe for relighting to occur.

Instead of providing two pistons 18 and 20 on the root of the reigniter member, the larger piston 18 may be dispensed with and the compressed air tapped from the compressor made to act on the upper face in Figures 2 and 3 of the piston 18 in order to move the reigniter member to its operative position, this always assuming that sucient pressure is available in the compressor to overcome the gas pressure in the combustion chamber. In this case the piston 18 and the bore 14 also constitute motive means operable to displace the reigniter member to its operative position, the piston 18 having the same eective piston area on each side.

We claim:

1. In a continuous combustion engine having a continuous combustion chamber, a reignition device comprising a carrier member mounted on the wall of the combustion chamber, a reigniter member carried by said carrier member and movable between an operative position in which the reigniter member projects into the zone of primary combustion in the combustion chamber and an inoperative position in which the reigniter member is withdrawn from said zone, motive means operatively connected with said reigniter member and operable to move the reigniter member to its operative position during normal running of the engine, and means` for preventing operation of said motive means when the rotational speed of the engine has fallen below a predetermined value.

2. In a continuous combustion engine having an air compressor and a continuous combustion chamber of the kind which operates with an internal pressure which exceeds the external pressure, a reignition device comprising a carrier member mounted on the wall of the combustion chamber, a reigniter member carried by said carrief member and movable between an operative position in which the reigniter member projects into the zone of primary combustion in the combustion chamber and an inoperative position in which the reigniter member is withdrawn from said zone, a uid motor connected to be operated by gas pressure in the combustion chamber to move said reigniter member from its operative to its inoperative position, a fluid operated means connected to be operated from its inoperative to its operative position to move said reigniter member by compressed air tapped from said compressor, a valve means controlling said uid operated means and comprising a two position valve, an electrical solenoid energizable to displace said valve to a position in which it allows compressed air to flow from said compressor to said fluid operated means, said valve, in its other position allowing the exhaust of air from said iiuid operated means, and spring means urging said valve into its said other position, said engine further comprising means for preventing operation of said motive means when the rotational speed of the engine has fallen below a predetermined value.

3. VIn a continuous combustion engine having an air compressor and a continuous combustion chamber of the kind which operates with an internal pressure which exceeds the external pressure, a reignition device comprising a carrier member mounted on the wall of the combustion chamber, a reigniter member carried by said carrier member and `movable between an operative position in which the reigniter member projects into the zone of primary combustion in the combustion chamber and an inoperative position in which the reigniter member is withdrawn from said zone, a uid motor connected to be operated by gas pressure in the combustion chamber to movesaid reigniter member from its operative to its inoperative position, a fluid operated means connected to be operated by compressed air tapped from said compressor and operative tomove -said reigniter member from from its inoperative to its operative position, a valve means controlling said fluid operated means and comprising a -two position valve, an electrical solenoid energizable to displace said valve to a position in which it allows compressed air to iiow from said compressor to said fluid operated means, said valve, in its other position allowing the exhaust of air from said iiuid operated means, and spring means urging said valve into its said other position, said engine further comprising means for preventing operation of said fluid operated means when the rotational speed of the engine has fallen below a predetermined value, said preventing means comprising supply means operable by the engine for supplying pressure iiuid at a pressure dependent upon engine speed, a pressure operated switch, duct means connecting said supply means to said pressure operated switch, said pressure operated switch being closable at the pressure supplied by said supply means when the engine is rotating above a predetermined speed and being connected to said electrical solenoid to prevent energization of said electrical solenoid when not closed.

4. In a continuous combustion engine having an air compressor a fuel pump of the multi-cylinder swash plate type connected to be driven from the engine by a positive drive and a continuous combustion chamber of the kind which operates with an internal pressure which exceeds the external pressure, a reignition device comprising a carrier member mounted on the wall of the combustion chamber, a reigniter member carried by said carrier member and movable between an operative position in which the reigniter member projects into the zone of primary combustion in the combustion chamber and an inoperative position in which the reigniter member is withdrawn from said zone, a iiuid motor connected to be operated by gas pressure in the combustion chamber to move said reigniter member from its operative 'to its inoperative position, a Huid operated means connected to be operated by compressed air tapped from said compressor and operative to move said reigniter member from its inoperative to its operative position, a valve means controlling said uid operated means and comprising a two position valve, an electrical solenoid energizable to displace said valve to a position in which it allows compressed air to ow from said compressor to said fluid operated means, said valve, in its other position allowing the exhaust of air from said uid operated means, and spring means urging said valve into its said other position, said engine further comprising means for preventing operation of said fluid operated means when the rotational speed of the engine has fallen below a predetermined value, said preventing means comprising' the piston block chamber of said pump, in which chamber, during operation of the engine, a centrifugal pressure head is developed which is a function of the rotational speed of the pump, a pressure operated switch, duct means connecting said chamber to said pressure operated switch, said pressure operated switch being closable at the pressure supplied by said chamber when the engine is rotating above a predetermined speed, and being connected to said electrical solenoid to prevent energization of said electrical solenoid when not closed.

5. Aircraft propulsion plant comprising a combustion chamber, a reigni-tion device movable between an operative position within the combustion chamber and an inoperative position substantially withdrawn from the combustion chamber, motive means connected to move said reignition device between said operative and inoperative positions, preventing'rneans operatively connected to said motive means, and sensing means for detecting a paramplant can safely be relit to a second condition in which it would not be Safe to relight the plant, said preventing means being operatively connected to said sensing means and being operable thereby when the sensing means detects the second condition of the parameter to prevent 10 said motive means moving `said reignition device into its operative posi-tion.

References Cited in the file of this patent UNITED STATES PATENTS Engler E Apr. 21, Webb Jan. 23, Macrae E Feb. 16, Macrae Nov. 15, Berkey July 22, McDougal e Aug. 18, Quinby Apr. 12,

Fowler et al. July 29, 

